1. Field of the Invention
The present invention relates to a deadweight calculating apparatus for displaying weight loaded on the bed of a vehicle for carrying cargo to prevent overload.
2. Description of the Related Art
As a general rule, a deadweight calculating apparatus for calculating the deadweight of a vehicle has sensors disposed adjacent to front and rear wheels of the vehicle to detect loads applied to the front and rear wheels to calculate the weight in response to signals output from the sensors. Moreover, the calculated deadweight is displayed on a display unit, if necessary. If the deadweight is too heavy, an alarm is issued.
By the way, in recent years, design has been attempted such that the conventional weight distribution, in which heavier loads are applied to the rear wheels, is changed and loads are equally applied to the front and rear wheels in order to improve the balance among the front and rear wheels.
Although the above-mentioned design of the vehicle is considerably advantageous from a viewpoint of improving safety during drive of the vehicle because the load balance between the front and rear portions of the vehicle can be kept equally in a state where a cargo is loaded on the vehicle, the ground pressure of the drive wheels, which are generally provided for the rear wheels, is too low when, for example, the vehicle starts at a slope, to result in slippage occurring attributable to running at idle.
Accordingly, the vehicles of the type having the improved weight distribution between the front and rear wheels have been increasingly provided with pressure-type start assisting units arranged to be operated when the vehicle is started at a slope or the like so that insufficiently low ground pressure of the drive wheels to the road surface is supplemented.
FIG. 5 is a schematic view showing the structure of a vehicle having the above-mentioned pressure-type start assisting unit. FIG. 5 shows a two-axle rear wheel portion of the vehicle in an enlarged manner.
Front wheels of the rear wheel portion designated by reference numeral 15 and rear wheels of the rear wheel portion designated by reference numeral 17 are respectively attached to the both ends of axles 27 through axle cases 25. The axle cases 25 are, through a slide plate 35, attached to two longitudinal ends of a leaf spring 33 having an intermediate portion received by a trunnion shaft 31 supported by a trunnion bracket 29 disposed on the lower surface of a platform frame 19.
A drive shaft 39 is, through a differential case 37, connected to the axle 27 of the rear-front wheels 15 so that the rear-front wheels 15 act as drive wheels because drive power is transmitted from an engine (not shown) through the drive shaft 39, the differential case 37 and the axle 27.
A pressure-type start assisting unit 41 for supplmenting the ground pressure of the rear-front wheels 15 against the road surface has an air-pressure or hydraulic cylinder 43 disposed between the platform frame 19 and the differential case 37, a fluid supply source (not shown) for supplying compressed air or pressurized oil, that is, fluid to extend and contract the cylinder 43, and a controller (not shown) for controlling supply of fluid from the fluid supply source to the cylinder 43.
When a switch of the start assisting unit 41 having the above-mentioned structure is operated to start the vehicle at, for example, a slope, fluid is supplied from the fluid supply source to the cylinder 43. Thus, the cylinder 43 is extended, thus causing the distance from the platform frame 19 to the differential case 37 to be extended. As a result, the rear-front wheels 15 is urged and pressed against the road surface so that the ground pressure of the rear-front wheels 15 against the road surface is raised. Thus, generation of slippage can be prevented.
By the way, when the foregoing start assisting unit 41 is operated, extension of the cylinder 43 results in reaction force applied from the road surface portion being applied to the slide plate 35, the axle case 25, the trunnion bracket 29 and the trunnion shaft 31, as indicated with arrows in FIG. 5.
However, since the foregoing elements are disposed in the portions in which sensors of the foregoing deadweight calculating apparatus have been disposed, there arises a problem in that calculations of the deadweight in accordance with outputs from the sensors, which are performed when the start assisting unit is operated, result in a value smaller than actual deadweight being undesirably obtained by a degree corresponding to the reaction force which is applied from the road surface portion because the cylinder 43 is extended.
When the obtained deadweight is arranged to be displayed or an alarm is arranged to be issued if the obtained deadweight is an overload level, there arises a problem in that incorrect deadweight is communicated or the alarm for sounding overload cannot be issued.